1. Field of Invention
The present invention relates to a polyurethane composition and methods for use of a polyurethane composition. More particularly, the present invention relates to a polyurethane composition having antimicrobial properties, and to methods for fabricating this composition for use in commercial settings, such as in a backing materials or padding for carpeting used hospitals and schools.
2. Background Art
In the floor covering industry, it is well-known that the installation of vinyl, tile or carpet provides microorganisms such as bacteria and fungi with a fertile environment for growth as the adhesives and the polymers used to manufacture the floor covering provide the organisms with abundant carbonaceous food sources. Where such floor coverings are applied over a padding and/or over highly alkaline surfaces, such as fresh cement sub-flooring, the microorganisms are provided with an even more favorable environment for growth. Over time, the effects of microorganism proliferation are manifested by a loss in the physical and/or aesthetic qualities of the flooring product and/or padding. In some instances, the effects are manifested by discoloration of the flooring product. In others, the effects are manifested by deterioration of the padding itself or of the adhesive backing to the extent that the adhesive no longer provides adhesion of the flooring product to the substrate surface. In still others, the effects are manifested by a combination of these conditions. The impact of these circumstances is most strongly felt in the carpet industry where carpet products and padding materials are used in commercial as well as residential, outdoor settings and in commercial and non-commercial vehicles.
Carpeting basically consists of a backing material having a carpet pile on one side of it. Carpet manufacturers, and more particularly tufted carpet manufacturers, typically use a binding material to attach a secondary backing material which could be a foam backing composition to complete the carpet product. The binding material that adheres secondary backing materials typically consists of a latex based adhesive that locks the carpet tufts to the backing material. The foam backing composition typically consists of a PVC plastisol, polyurethanes, EVA or latex that creates a cushion which increases walking comfort and enables a reduction in the amount of carpet pile used to create the carpet's cushion. Carpet padding is typically fabricated from materials similar to those used for foam backing compositions.
Polyurethanes are typically preferred for the formation of the secondary backing material as, though more expensive than latex, they provide product advantages which allow the carpet to maintain its appearance and backing integrity. These advantages notwithstanding, carpet manufacturers have experienced difficulty in using polyurethanes in backing material fabrication where attempts have been made to incorporate an antimicrobial agent into the backing material. Some antimicrobial agents are solids in their naturally occurring state and, as such, are difficult to manipulate. In a dry state, the chemical properties of the agents can disrupt the catalytic reaction required for formation of the polyurethanes. Accordingly, it has been difficult, if not impossible, to effectively incorporate dry antimicrobial agents into the polyurethane foam backing material used to fabricate the carpet products and carpet padding that is manufactured and sold.
The art has looked to liquids for incorporating an antimicrobial agent into polyurethane compounds. One such method incorporates an arsenic based antimicrobial agent, such as OBPA or vinyzene, dispersed in a glycol, to form a polyurethane product. Still other methods and products known in the art are disclosed in U.S. Pat. No. 5,114,984 issued to Branch, et al. ("the '984 patent"); U.S. Pat. No. 5,319, 000 issued to O'Connor, et al.("the '000 patent"); and, U.S. Pat. No. 5,639,803 issued to Anderson, et al. ("the '803 patent").
The '984 patent discloses a method for producing an antimicrobial polyurethane foam product wherein the biocide is liquified in the formation of the foam product. The '803 patent discloses a method for liquefying a biocide to form a preliminary dispersion which must then be heated to an elevated temperature and cooled to form the claimed dispersion. The '000 patent provides a method for forming a biocide by combining it with a non-polyurethane plastisol prior to heating and cooling the foam product in a manner similar to that described in the '803 patent.
Each of the methods disclosed in these patents requires the use of water to complete the liquefaction step and produce polyurethane foam product. The use of water to produce the polyurethane product formed by these methods compels the use of more isocyanate to combine with the polyol in mixture and insure completeness of the polyurethane forming reaction. Moreover, at least one of these methods also requires the addition of other chemicals to insure that the biocide remains suspended in the liquid dispersion so that it may be stored over an extended period of time.